We have to admit we're impressed. Here are the five we liked the best:

1. In their very first hackathon of 2012, having just moved into their new Menlo Park, Calif., campus, they painted a giant QR code on the roof of a building. It originally pointed to a spoof listing for a "QR code painter" job, but now points to a page about the project.

Can you spot the code in this aerial shot of the campus?

2. Engineer Paul Tarjan mapped out data about which users liked which NFL teams' Facebook pages across the country, and found out some surprising things—like how the Upper Peninsula of Michigan has a lot of Green Bay Packer fans, instead of being loyal to the Detroit Lions.

3. Using open-source hardware from a company called Arduino, the team built a display of flashing lights which warned about spam levels on Facebook. In addition to email alerts, the spam fighters now get red, yellow, and green lights telling them when they need to step in and do battle.